Improper Handling of Case Sensitivity in fast-uri - CVE-2026-86472
Published: September 16, 2026
Vulnerability identifier: #VU150187
CSH Severity: Medium
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-86472
CWE-ID: CWE-178
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass host allowlist or denylist checks.
The vulnerability exists due to improper handling of case sensitivity in the fast-uri host parsing, normalization, and equality functions when processing scheme-relative references containing percent-encoded uppercase unreserved host octets. A remote attacker can supply a crafted scheme-relative URL to bypass host allowlist or denylist checks.
The evading hostname resolves and routes to the same host intended to be restricted.
Affected software
fast-uri
How to mitigate CVE-2026-86472
Install security update from vendor's website.
fast-uri - addressed in versions 2.4.7, 3.1.8, 4.1.5